Human umbilical cord mesenchymal stem cells reconstruct the vaginal wall of ovariectomized Sprague–Dawley rats: implications for pelvic floor reconstruction

Vaginal structural defects are involved in pelvic organ prolapse (POP). We tested whether mesenchymal stem cell (MSC) therapy can repair the weakened vaginal wall of POP patients as a novel POP treatment. Ninety-six ovariectomized rats were divided into 4 groups (n = 24/group): saline (sal), collagen (col), sal + MSC, and col + MSC groups. Two weeks after ovariectomy, rats received subepithelial injection of 0.3 ml saline, 0.3 ml collagen I gel, and 0.3 ml saline: 3 × 106 human umbilical cord mesenchymal stem cells (HUMSCs), or 0.3 ml collagen I gel: 3 × 106 HUMSCs into the anterior vaginal wall. Eight additional rats underwent in vivo bioluminescence imaging (BLI) to evaluate in vivo cell viability. The BLI signal disappeared within 1 week after MSC injection, and no in vivo MSC differentiation was found. Collagen I content was significantly lower at 4 and 12 weeks in the two MSC groups than in the sal and col groups, while collagen III was significantly higher (P < 0.001). The fraction of smooth muscle in the nonvascular muscularis increased significantly in the two MSC groups at 12 weeks (P < 0.001). ACTA2 mRNA in the col + MSC group was significantly higher than that in the sal group at 2 and 4 weeks (P = 0.042 and P = 0.040). mRNA levels of angiogenic factors (bFGF or VEGF) in the two MSC groups were significantly higher than those in the sal and col groups at different time points. HUMSCs normalized the fibromuscular structures of the vaginal wall of ovariectomized rats potentially through a paracrine effect.